The disclosure relates to a blowout preventer (BOP) stack. More particularly, the disclosure relates to a BOP stack with an interface that, when the BOP stack is installed on a wellhead, allows access to the well bore.
As is well known, a blowout preventer (BOP) stack is installed on a wellhead to seal and control an oil and gas well during drilling operations. A drill string may be suspended inside a drilling riser from a rig through the BOP stack into the well bore. A choke line and a kill line are also suspended from the rig and coupled to the BOP stack.
During drilling operations, drilling fluid, or mud, is delivered through the drill string, and returned up an annulus between the drill string and casing that lines the well bore. In the event of a rapid influx of formation fluid into the annulus, commonly known as a “kick,” the BOP stack is actuated to seal the annulus. The kick may be circulated up to rig processing equipment. Alternatively, heavier drilling mud may be delivered through the drill string, forcing fluid from the annulus through the choke line or kill line to protect the well equipment disposed above the BOP stack from the high pressures associated with the formation fluid. Assuming the structural integrity of the well has not been compromised, drilling operations may resume. However, if drilling operations cannot be resumed, cement or heavier drilling mud is delivered into the well bore to kill the well.
Were the BOP stack to fail to actuate in response to a surge of formation fluid pressure in the annulus, a blow out may occur. The blow out may result in loss of life to those aboard the rig, damage to the well equipment and/or the rig, and damage to the environment. In such circumstances, apparatus and methods that enable rapid access to the well bore are desirable.